Coming into a year in which they lost sharpshooter Ray Allen, one concern of the Celtics was how the team’s new offense would operate with a slew of new perimeter players on board. But, as it turns out, the Celtics’ problem in the first month of the season has had nothing to do with the offense—it is a decidedly defensive problem, with teams able to rack up easy baskets inside while also getting good looks from the perimeter.

The Celtics are allowing 46.3 percent shooting from the field this year, which ranks 26th in the league. They also rank 26th in defensive efficiency (a measure of points allowed per 100 possessions), after leading the league in that category last year and finishing third the previous year.

Boston Celtics guard Rajon Rondo is known as a good defender in league circles, yet his team has struggled to stop teams thus far. (AP Photo)

All of this is troubling to coach Doc Rivers, who has prided himself on his team’s defensive tenacity since the acquisition of Kevin Garnett in 2007. The absence of the Celtics' best on-ball defender, Avery Bradley, also is a point of concern. Rivers does not necessarily think that the Celtics’ deficiencies have been all about not playing hard enough—they simply have not been smart in their approach, particularly in pick-and-roll coverages.

“I think we’ve got to do our coverages better, just bottom line,” Rivers said. “Playing harder and all that, that sounds great. That’s what everyone says when you lose, ‘You’ve got to play harder.’ Well, we’ve got to play smarter, we have to know our coverages better, and when that happens everybody is on the same page and it allows our rotations to be freer, it allows our bigs to get back to the paint. So I thought it was a lot of that.”

The Celtics are a veteran team and have been known to pace themselves in the early part of the year. But with an influx of nine new players on the roster, Rivers had hoped that things would come together faster and that the Celtics would be a better defensive team by now. And though there is a lot of the year left, the Celtics have to be aware that the resurgence of the Knicks and Nets means they can’t take a high seed in the Eastern Conference for granted, because there will be a fight for the Atlantic Division.

“Everybody’s pretty much upset about it,” new guard Courtney Lee said. “For the goals we have, winning far and winning big, and the playoffs and we’re trying to get home court advantage and these are the games we can’t let slip away. We’re definitely frustrated and upset about that.”